The present invention relates to an improved data transmission system, and in particular, relates to a digital type multi-channel modulation and/or demodulation system which transmits digital data through a band-limited analog type transmission line.
A multi-channel orthogonal VSB (Vestigial SideBand) transmission system has been known as one of the data transmission systems using a band-limited analog type line. The prior modulation and/or demodulation system for the above orthogonal VSB system comprises a plurality of the transmission filters for each channel in a modulator and a correlation detector in a demodulator, and is disclosed in R. W. Chang;
"Synthesis of Band-Limited Orthogonal Signals for Multi-channel Data Transmission," B.S.T.J., 45, 10, p. 1775 (Dec. 1966). The present applicant has already filed some patent applications which improve Chang's device.
In the prior system proposed by Chang, a data transmission system with a theoretical transmission speed could be realized without suffering from a inter-symbol interference and/or a inter-channel interference, if an ideal line equalization and a modem were obtained. However, said theoretical speed could not be practically obtained due to some interferences by the various error factors.